/Engine/Plugins/Protocols/MQTT/Source/MQTTCore/Public/MQTTSubsystem.h
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, BlueprintPure, Category="MQTT") static [FString](API\Runtime\Core\Containers\FString) GetPayloadString ( const [FMQTTClientMessage](API\Plugins\MQTTCore\FMQTTClientMessage) & InClientMessage )